Work machines such as loaders and the like are used for moving mass quantities of material. These machines have work implements consisting primarily of a bucket linkage. The work bucket linkage is controllably actuated by at least one hydraulic cylinder. An operator typically manipulates the work implement to perform a sequence of distinct functions to load the bucket.
In a typical work cycle, the operator first positions the bucket linkage at a pile of material, and lowers the bucket downward until the bucket is near the ground surface. Then the operator directs the bucket to engage the pile. The operator subsequently raises the bucket through the pile to fill the bucket, then the operator racks or tilts back the bucket to capture the material. Finally, the operator dumps the captured load to a specified dump location. The work implement is then returned to the pile to begin the work cycle again.
The earthmoving industry has an increasing desire to increase the productivity of the work cycle. Although high rimpull ratings of the machine have been found to generally increase the productivity of the work cycle (rimpull is known as the tractive force that a machine is able to generate), it has been found that a machine producing high amounts of rimpull can negatively effect certain portions of the work cycle. For example, during the digging portion of the work cycle, machine rimpull has been found to oppose the lift force of the work implement, which negatively effects the ability of the machine to lift a load of material. The present invention is directed toward overcoming the problems associated with producing high amounts of rimpull during the digging portion of the work cycle.